Dual power microscope

ABSTRACT

A dual power microscope comprises an assembly of eyepiece and objective lenses in fixed relationship to one another and an assembly of specimen stage and a negative relay lens in fixed relationship to one another, the two assemblies being coaxially relatively slidable and the relay being disposed between the objective and the eyepiece. When the eyepiece-objective assembly has been pulled away from the specimen stage a low magnification image is seen; and when pushed toward the stage a high magnification image is seen.

D United States Patent 1191 1111 3,743,377 Rosenberger [4 July 3, 1973DUAL POWER MICROSCOPE Pn'ma Examiner-David H. Rubin 7s 1 1 1 u E. R h I1 men or mnbemr Roe ester Attorney-Frank C. Parker et al.. [73]Assignee: Bausch & Lomb Incorporated,

Rochester, NY. [57] ABSTRACT Filed! J 1972 A dual power microscopecomprises an assembly of [211 App! NOJ 217 811 eyepiece and objectivelenses in fixed relationship to one another and an assembly of specimenstage and a negative relay lens in fixed relationship to one another, Cl350/37, 350/46, 35 the two assemblies being coaxially relativelyslidable [51 Int. Cl. G02b 7/04 and the relay being disposed between theobjective n [58] Field of Search 350/37, 40-44, the eye iee When theeyepiece-objective assembly 350/34146 has been pulled away from thespecimen stage a low magnification image is seen; and when pushed towardRdfl'wm the stage a high magnification image is seen.

UNITED STATES PATENTS 3,353,391 11/1967 Rosenberger 350/43 x 2 Chums 3Drawmg Pmsmemm a ma 3.743.377

SHEET 2 BF 2 F0 1| L4. Hi m- CROSS-REFERENCES TO RELATED APPLICATIONSThe present invention is related to the invention described inconcurrently filed and commonly assigned application Ser. No. 217,812 ofDonald D. White for Dual Powered Microscope.

BACKGROUND OF THE INVENTION 1. Field of the Invention The field of theinvention is variable magnification optical systems, and morespecifically dual power optical systems having a finite objectconjugate.

2. Description of the Prior Art Inexpensive microscopes for children inelementary schools have been mostly limited to fixed power instruments,which restrict the extent to which a childs awakening interest in theminute, natural world about him can be stimulated. While there have beensome dual power instruments which afford both low and high power views,they have suffered in the main from either high costs if their imagequality was good, or poor image quality if their costs approached whatour school districts can afford.

Axially movable intermediate lenses between fixed objective and eyepiecelenses are known in the telescope art where the object conjugate isinfinite. See, for example US. Pat. No. 2,479,792 to R.B. Tackaberry. Inmicroscopes, where the object conjugate is not only finite, but usuallyquite short, at least two moving intermediate lenses, each following adifferent path, have been used. Since the actuating mechanisms for suchcomplex movements are quite costly there is little prospect for theirbeing used in inexpensive microscopes.

SUMMARY OF THE INVENTION A good, but inexpensive, dual power microscopewhich would permit a child to obtain both an overall macroscopic view ofa specimen at a relatively low power and a detailed, structuralmicroscopic view at a substantially higher power would therefore be amost welcome development.

In order to achieve a dual power microscope of excellent image qualitywhile retaining the most simple possible mechanical accommodations forit I have worked out a set of optical conditions under which amicroscope may consist of only two basic units which, with a singlepositive relative movement of the units between two discrete positions,changes magnification. One unit includes both an objective lens and aneyepiece lens in fixed spatial relationship to each other. The otherunit includes a specimen stage and a relay lens in fixedspatialrelationship to each other, the relay lens being disposed betweenthe objective and the eyepiece. The microscope is completed with slidemeans for axial adjustment of the two units, and base and housing means.Any of the.base, slide and housing means might well form a portion ofeither or both basic units of the microscope.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an optical schematic diagramof the microscope of my invention at low and high power settings,showing the relationships between them.

FIG. 2 is a sectional profile of a microscope demonstrating themechanical development of my invention.

FIG. 3 is a side view of a part of the microscope, showing the means forrelative sliding of the two main assemblies.

DETAILED DESCRIPTION OF THE INVENTION 1. Conditions for the Design Lowercase letters denote conditions at the lower magnification setting.

Capital letters denote conditions at the higher magnification settings.The objective lens 52 and relay lens 32 are designated lenses A and Brespectively.

The object distances d, andD, are negative when the object lies to theleft of lens A.

The objective and eyepiece are mechanically linked and move in a 1:1ratio over the distance C from the magnification settings m to M and -Cfrom M to m.

The focal lengths of the first two lenses are designated F and Frespectively.

When the object to image distance k and the magnifi cation m are chosen,the object distance d,, lens separation t and image distance d arepredetermined by the following relationship:

Simultaneously, the higher magnification M, the object to image distanceK and the objective-eyepiece motion C are predetermined by the followingrelationship:

It follows from FIG. I that T K D, D

2. DESCRIPTION OF THE PREFERRED EMBODIMENT A. OPTICAL DESIGN nificationssignify that the images as magnified are in- B. MECHANICAL DESIGN InFIG. 2, the microscope is designated generally as 10. A support pillar12 rises from a base 14 and carries a specimen stage 16 as well as amicroscope receiving tube 18. The interior of the tube 18 is formed todefine a helical groove 20. A relay carrier 22, also of tubular shape,is receivable in the tube 18. The carrier 22 is molded around a pin 24which is cooperative with the groove to advance the carrier 22 along theaxis of the tube 18 when the carrier is rotated relative to the tube.The exterior of the carrier 22 defines a plurality of circumferentialgrooves 26 in which O-rings 28 are fitted. The O-rings 28 are slightlyoversized relative to the outline of the grooves 26 and are preferablyof a resiliently deformable material (such as silicone rubber) chosenfor a sliding compatibility with the interior walls of the receivingtube 18. The O-rings 28 serve to hold the carrier 22 centered on themicroscopes axis 30 and also are the bearings which permit the carrier22 to be rotated by means of the pin 24 and the helical groove 20.

A relay lens 32 is pressed into a cooperative aperture formed in a relaylens mounting cell 34 and the latter is fastened by means of the eyelets36 to the carrier 22.

Meanwhile a tubular slide 38 defining circumferential grooves 40 inwhich are fitted O-rings 42, is coaxially received in an interior borein the relay carrier 22, the O-rings 42 being of pliant, resilientlydeformable material and serving to center the slide to the axis 30 andto provide a slide bearing surface for the slide 38 to move axiallywithin the carrier 22.

Viewed from the side, as in FIG. 3, the slide 38 is seen to define arectangular aperture 44 of a width cooperatively corresponding with thevertical sides of the relay lens cell 34.

The slide 38 serves as a mount for the eyepiece lenses 46, 48, and forthe objective lens cell 50. The objective lenses 52 are retained in acentral bore of the cell 50, coaxial with the axis 30 of the microscope,by a member 54 which additionally serves to define an aperture stop 56.A stop screw 58 is threaded into a second bore 60 located eccentricallyin the cell 50.

During assembly the relay lens cell 34 is first loosely placed in theaperture 44 of the slide 38, which is then placed within the interiorbore of the carrier 22 and the relay cell 34 is then rigidly affixed bymeans of the eyelets 36 to the carrier 22. Thus, the slide 38 isconstrained within the carrier 22 for sliding motion through anexcursion, which is defined at the upper end by the top of the relaylens cell 34 interfering with the top of the aperture 44, and at thebottom by the adjustable stop screw 58 bumping the bottom of the relaylens cell 34. The microscope assembly is completed by insertion of therelay carrier 22 into the microscope receiving tube 18, the pin 24 beingguided into the helical groove 20.

Thus, when fully assembled the slide 38 serves to hold the objectivelens 52 in fixed spatial relationship to the eyepiece lenses 46, 48,while the support pillar 12 serves to hold the relay lens 32 in fixedspatial rela tionship to the specimen stage 16 (it being appreciatedthat the carrier 22 may be rotated and moved along the axis 30 forfocusing of the microscope, but that once focused the conjugate from therelay lens 32 to the stage 16 remains fixed during the actual use of themicroscope).

As shown in FIG. 2, with the tip of the stop screw 58 engaged with thebottom of the relay lens cell 34, the microscope is in the low powerposition. When the objective lens and eyepiece lenses incorporated inthe slide 38 are moved downward as a unit, by pushing the slide 38downward until the objective lens cell occupies the position shown indotted outline 62, the microscope is brought to the high power position.

In practice the high power position is realized by depressing the slide38 until the top of the aperture 44 is engaged with the top of the relaylens cell 34. The carrier 22 is then rotated to bring a specimen slideof standard thickness on the stage 16 into focus, it being recalled thatat high power the focal envelope is relatively narrow. The slide 38 isthen raised until the image is observed to be in focus in the eyepiecefocal plane 64 at the low power position, the low power focal envelopebeing significantly wider than at the high power setting. The stop screw58 is then adjusted to meet the relay lens when a condition of sharpestfocus is observed. The range of travel of the slide 38 then correspondsto the dimension C discussed above under the heading Conditions for theDesign.

I claim:

1. A microscope having, in alignment along an optical axis:

a. a stage and relay assembly comprising a specimen stage, relay lensmeans and mechanical linkage means for disposing said relay lens meansin fixed position relative to said specimen stage; an eyepiece andobjective assembly comprising objective lens means, eyepiece lens meansand mechanical linkage means for disposing said eyepiece lens means infixed position relative to said objective lens means; and

c. base, slide and housing means for slidably and coaxially mountingsaid two assemblies, with said relay lens means disposed between saidobjective lens means and said eyepiece lens means, for relative motionalong said axis through an excursion, said excursion defining at leasttwo positions of optical cooperation among said objective lens means,said relay lens means, said eyepiece lens means and said specimen stage,one for low magnification viewing and one for high magnification viewingof a specimen on said stage.

2. The microscope of claim 1 wherein said objective lens means has afocal length F and said relay lens means has a focal length Fmeasurements along said optical axis are taken from said objective lensmeans positive toward the image side, low magnification conditions aredesignated by small case letters, high magnification conditions aredesignated by large case letters;

0,, d, represent the object distances;

T, t represent the separations of the objective lens means from saidrelay lens means;

D D represent the separation of the relay lens means from the eyepiecefocal plane;

K, k represent the distance from the object plane to the eyepiece focalplane;

C represents the length of said excursion measured in the direction ofthe image;

M, m represent the degree of magnification of a specimen in the objectplane measured in the eyepiece focal plane;

1. A microscope haviNg, in alignment along an optical axis: a. a stageand relay assembly comprising a specimen stage, relay lens means andmechanical linkage means for disposing said relay lens means in fixedposition relative to said specimen stage; b. an eyepiece and objectiveassembly comprising objective lens means, eyepiece lens means andmechanical linkage means for disposing said eyepiece lens means in fixedposition relative to said objective lens means; and c. base, slide andhousing means for slidably and coaxially mounting said two assemblies,with said relay lens means disposed between said objective lens meansand said eyepiece lens means, for relative motion along said axisthrough an excursion, said excursion defining at least two positions ofoptical cooperation among said objective lens means, said relay lensmeans, said eyepiece lens means and said specimen stage, one for lowmagnification viewing and one for high magnification viewing of aspecimen on said stage.
 2. The microscope of claim 1 wherein saidobjective lens means has a focal length FA and said relay lens means hasa focal length FB, measurements along said optical axis are taken fromsaid objective lens means positive toward the image side, lowmagnification conditions are designated by small case letters, highmagnification conditions are designated by large case letters; D1, d1represent the object distances; T, t represent the separations of theobjective lens means from said relay lens means; D2, d2 represent theseparation of the relay lens means from the eyepiece focal plane; K, krepresent the distance from the object plane to the eyepiece focalplane; C represents the length of said excursion measured in thedirection of the image; M, m represent the degree of magnification of aspecimen in the object plane measured in the eyepiece focal plane; a(1-m)2/m; Q d1 + t - d2; R (FA + FB + d1 - d2)t - (FA + d2)d1 - (FA -d2)FB; t 1/2 ( k + or - Square Root k2 - 4 FA FB a - 4k(FA + FB) ); d1 -FA ( k - t(1-m) )/FA (1-m) + m t ; d2 k + d1 - t; C -Q + or - SquareRoot Q2 - 4R/2; M (FA/D1 + FA) X (FB - D2/FB); D1 d1 + C; D2 d2 - C; Kk - C; and T K + D1 - D2.